Process of making cement.



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ARTHUR C. SPENCER AND EDWIN C. ECKEL, OF WASHINGTON. DISTRICT OFCOLUMBIA.

PROCESS OF MAKING CEMENT.

No Drawing.

. To all whom itmay concern:

Be it known that We, ARTHUR G. SPENCER and EDWIN C. ECKEL. citizens ofthe United States, residing at \Vashington. in the District of Columbia.havevinrentecl certain new and useful Improvements in Processes oiliiaking Cement. of which the following a specification.

This invention relates to processes oi making; cement; and it comprisesmethod. making a cementitioua (aiiiiposition wherein a, natural ironsilicate is heated with calcareous material until elinkering iseffected: all as. more lull hereinafter set f rth and as claimed.

While the proximate constitution of ordinary Portland cement clinker isnot delinitely known. it is usuall) assun'ied to be. in substance. amixture of aluminate of lime and silicate of lime; aluminum sesquioxidplaying the part of an acid conetituent. Other seequioxide can. replacethe alumina in whole or in part and where toe replacement is; or 'lerrir oxicl a dense dark Cement is producwl h ch has valuable propertiesfor many purposes; as for use in sea-water.. sewer con: .ructiou and inmines the waters of which and especially sul'tnric acid and sulfates. iiishowever somewha (liiilcult to make this terri ccemen't technicallyunder ordinaifl; cement kiln. condition from a mixture of the ordinaryform at silica. with iron ore and lime or limestone since the reactionis not read) and high 1" .peratures are irmpaisite; this hightemperature in turn terulina to produce a clinker in cone para i. if;large. mas, s which are (lillicult to conunivmle. iron. cement being"usually hard. i iilica in the ordinary l'orm oi sandy or quart-rosesilica and the quartozose ganglia of ores is very little rr tire undercement kiln rourlilionu. Ferric oxiil pm xv docs not readil) comliiuewith lime and silica and, :part from the dililcultv of causing reactionsin any comps:ratirely iniusihlr po der, in any artificialmixture ofthese bodies the mutual contact and the unifornv 'ity and intimacy ofadmixture are impen i'ect. in o: r to obtain any union at all with amixture oi lime. iron ore. and sand. the ingredients nun-4t he reduce"to an impalpalile state at :uibiliv 1 an operation which expensive. 'lll.ri obrioua. the conditions for makin such a neni: are not as .avorah asIn n t vac are ot' ordi Specification of Letters Patent.

Patented Dec. 19,1916.

Application filefl Shine 6, 1910. Serial No. 565,387.

is already in chemical combination with one ol the other ingredients ofthe mixture: the silica. in a chemical combination admixture of coursemolecular. In making Portland cementfrom clay, the lime has merel) toreact with the aluminum silicate whereas in making a cement from the(lesrribed mixture of iron ore. sand. and lime the lime must probablymostly first combine with the silica and then the silicate react withthe lerric oXid. This reaction is not ready. Moreover. oxid iron oresare relatively expensive. and in this country, are not usuall availablenear the seaboard where the iron cement is most in demand. \Ve harediscovered that any of the natural silicates of iron can be veryadvantageously employed to produce iron cement. In such silicates ofiron the silica and the mild are oi course in molecular contact; are inan admixture which is not possible to produce mechanically. even hv themost intimate mixing. With these silicates of iron therefore thereaction. with lime is quick and ready and does not require unduetemperatures. These natural silicates are soit and can readily bereduced, to line uniform powders well suited for miningwith the calcareous materials while where containing ferrous iron. on oxidation onheating in contact With calcining limestone in thefirst stages of thecement making: operation they tend to break down and be ome even liner.'lhe. industrial waste sings and similar materiale derived from copperand lead 'lurnacess. iron refining operations and the like zlli notonlyunduly hard but have no constant composition while the) usually containmany other things than iron silicates. The natural silicates. Such, asglauconite. on the other hand. occiir'in relatively Soft granules whichare readily rommimlted and. as readily intimately admixed with the othercomponents of the cement mixture. And these silicates occur i large bedsof relatively uniform composition. They are o'i'wlinarily free ofundesirable metallic oxirls such as the oxirls of the heavy metals.(llinker can readily be produced from these natural silicates of iron inadmixture with lime iitorclinary cement kilns. such as rot rv kilns. andb}: the ordinarv procedures.

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iron is basic and in a cement mixture tends more or less to replace hmewhereas the ferric oxid 1s a sesquioxld and tends to replace alumina;that is, it is an acid constituent. With certain of these naturalsilicates there is given the possibility of recovering valuableby-products which add materially in cheapening the cost of operation;'For this purpose, the silicate known as glauconite is partihularlydesirable since it contains considerable percentages of potash which maybe fumed ofi. and recovered as a by-product. large deposits along theseaboardfand in manyplaces the glauconite is associated with shell marlwhich may be used as a source of lime. For the present purposesglauconite may be regarded as adouble silicate of potassium and iron,the proportion of potash varying between 4: and 16 per cent. Uponheating a mixture of this silicate with lime, limestone, or marl, anumber of reactions occur. The limestone loses its carbon dioxid, or iscalcined, any ferrous iron present becomes ferric iron by oxidatioh andthe ferric iron, lime and silica unite to form a clinker. In thisoperation the potash is, or may be, largely expelled by volatilizationas fumes which may be caught and recovered.

A good iron cement may be made by clinkering a mixture of glauconite andlime, using lime in suilicient amount to unite with the acid bonds ofthe silica and of the ferric oxid and alumina present. Any ferrous oxidpresent in the mixture. will be oxidized to ferric oxid prior toclinkering. A composition of good cementitious properties may be madefrom mixture giving about 60456 parts lime, 813 parts of ferric oxid andalumina and the residue silica, etc. The lime may be mixed with theglauconite as such or in the form of limestone shells, or the like,calcium carbonate being calcined and converted to lime during theoperation.

The apparatus used may be an ordinary rotary cement kiln. It is lessdesirable to perform the operation upon the briqueted material in theolder types of stationary cement burning devices for the reason thatthis does not give an opportunity for free oxidation of such' ferrousiron as may be present or for free evolution of potash in fuming oil thelatter. The potash fumes evolved during the operation. can be caught andrecovered in the kiln dust. As this dust is largely caustic andcarbonated limc it is in and of itself agood fertilizer and itsfertilizing value increases in direct proportion to the amount of potashwhich can be recovered with it. Most of the potash is evolved in the hiher temperature stages of the operation an to secure a good recovery ofthe potash it is better to maintain the material at a clinkeringtemperature for some This mineral ocglrs in length of time. Thisclinkering temperature should however not be excessive. Other fthingsbeing equal, the evolution of potash {at any given temperature isproport onal to the surface of material exposed to the kiln gases and tothe time of such exposure. It is therefore better to use a rotary kilnwith powdered material and give a protracted exposure at a temperatureand under conditions Where the clinkers will not agglomerate into largemasses or fuse down. The powdered mixture travels down through a 1'0-tary kiln as a thin agitated stream underlying a countercurrent of flameand flame gases giving ideal conditions for fuming 0E potash. Operatingin a rotary kiln, the rotation and thermal conditions should thereforebe so controlled in the clinkering zone as to give a ood period ofexposure Without forming arge bodies of clinkers. The

formation of such large bodies is further more inadvisable for thereason stated that iron cement is relatively hard and difficult togrind. Since chlorid of potassium is rather more volatile than theoxidized compounds of potassium, the recovery of potash may befacilitated by mixing a small proportion of calcium chlorid with theoriginal mixture. Under the influence of the clinkering heat the chlorinand the potash are displaced and fumed off as potassium chlorid. Whetherthe fumes are evolved as chlorid or as oxid, carbonate or other salts orcompounds formed under the influence of the fiame gases and vapors, thepotash under well known laws largely tends to condense upon the dustparticles in the gases going through the kiln and is therefore carriedover the dust chamber.

While, as stated, in using glauconite the operation can be performed inthe ordinary type of rotary kilns and by the ordinary processes it ismuch better to perform the operation in a methodical manner. By so doinga number of advantages are gained. The mixture may first be calcinedalmost completely. At the comparatively low temperature of calcinationrelatively little potash is evolved and the dust coming from thispartial calcination contains little potash. In the calcining operationthere is always a considerable evolution. of dust and this dust iscarried forward by the kiln gases. Calcination is a low temperatureoperation in which large volumes of gases are necessarily employed andthe larger the volume of gases the more diflicult the complete recoveryof potash fumes. By now resummg and completing the calcination. withsubsequent clinkering as another stage in the operation, comparativelylittle dust is evolved and with this small quantity of dust is recoveredall the potash which is evolved in the clinkering operation. Clinkeringis a high temperature operation in which but lZi a small volume of gasesneed be employed so that the evolved potash is not distributed through alarge body of gases. A dust-like material is thus obtained which carriesmuch more potash and is much more valuable as a fertilizer. In practicethe cement mixture may be passed down through a'rotary kiln, which maybe separately fired, and. there partially calcined. The partiallycalcined material may now be transferred to another rotary, theca-lcination completed and the calcines clinkered. For this operation avpair of communicating rotary kilns may be employed the kilns in whichthe final calculation and the clinkering are effcctedbeing provided withseparate dust chambers. The clinlizering kiln may be pro vided as usualwith flame producing means using powdered coal, gas, oil, etc. The hotgases from the clinkering kiln may be transferred to the calcining kilnand used for efiecting the calcination, or, as stated, the calciningkiln may be separately fired. The natural silicates often containconsiderable water. If desired the mixture may be first roasted anddehydrated in still another l'riln,

the waste gases from the calcining kiln being employed for this purpose.Or the roasting and dehydration may be effected in the calcining kilnproper.

The caleination may of course be performed in av rotary and theclinlrering' in a stationary furnacez or the reverse. The material mayhe first calcined in a vertical kiln and then finished in a rotary. Orthe lime may be first calcined in the ordinary manner and then mixedwith the greensand.

Many other modifications are possible within the purview of ourinvention.

This methodical method of treatment is also useful in making ordinaryalumina cement and recovering potash where polassifcrous silicatessuclras feldspar, mica, gram ite, etc, form a part of the raw materials.These potassiferous mineral materials may be mixed with lime orlimestone in the manner described and methodically treated to in akecement and fume off potash in the same manner as just described for theglauconite mixture, the barren dust due to the first part of thecalcining operation, and the richer potassit'erous dust due to thefinishing calcination and the clinkering'being separately collected. I

(lreenalite is another natural iron silicate which, though notpotassiferous, is regarded as a. variety of glauconite and may be usedin the present invention.

Mixed cements may be made by using various natural silicates containingboth iron and alumina and for some purposes cei'nents of inlerinediatecomposition are advantapmous. Many of these mixed silicates are,law/ever, rather hard and they are generally massive. Glauconite andgreenalite are of better physical consistency for the present purposes.

What We claim is 2- s: 1. The process of preparing a cement clinker andby-products which comprises heating a potassiferous natural iron siica'te of the glauconite type with a calcareous material untilclinkering ensues and the potash is fumed oil' and recovering the potashevolved in the heat treatment.

2. The process of preparing a cement clinker and byproducts whichcomprises heating a potassiferous natural iron silicate of theglauconite type with a calcareous material until clinkering ensues andthe potash is fumed of? and recovering the potash evolved in the heattreatment together with evolved dust.

3. The process of preparing a cement clinker and recovering potash whichcomprises heating together a charge composed substantially oi calcareousmaterial and a. mineral ccanprisiug a double silicate of potassium andcement-forming oitid until clinkering ensues and fumes or potassiumcompounds are evolved, the heating being continued until a substantialproportion of the potassium compounds present are removed from themixture, and recovering the fumes of potassium compounds evolved in suchclinkering.

4. The process of preparing a cement clinker and recm eriug potash whichcomprises heating together a charge composed substantially of calcareousmaterial and a niineral comprising a double silicate of potassium andcement-forming oXid until clinkering ensues and fumes of potassiumcompounds are evolv'd, the heating being continued until a substantialproportion of the potassium compounds pres t are removed from themixture, and recovering the potassium compounds evolved in suchclinkering together with evolved dust.

5. The process of preparing a cement clinker and by-products whichcomprises heating adouble silicate of potassium and :1. cement-formingoxid together 'ivith calcareous material until cliulreriug; ensues, suchheating being done in a plurality of steps and being so controlled inonesuch step as to liberate more potash than in another such step, and thedust or dust and fume evolved in each such step being separatelycollected.

(S. The process of preparing a cement clinker and lay-products whichcomprises heating a potassit'erous natural iron silicate of theglauconite type together with calcareous material until clinkeringensues, such heating being done in a plurality oi steps and losing socontrolled in one such step as to liberate more potash tha r in anothersuch stem and the dust or dust and fume evolved in each such stop beingseparately collected.

7. The process of preparing an iron ccment which comprises heating acement mixture comprising glauconite and calcareous material untilclinkering ensues.

8. The process of preparing an iron cement and by-products whichcomprises heatmg a cement mixture comprising glauconite and calcareousmaterial until clinkering ensues and collecting the evolved potash withthe evolved dust.

9. The process of preparing an iron' oement and by-products whichcomprises heat- .ing a cement mixture comprising glauconite andcalcareous material until clinkering ensues and collecting the evolvedpotash with the evolved dust, such heating being performed in aplurality of stages and the dust from each stage being separatelycollected.

10. In a process of making cement clinker and by-products, the processwhich comprises heating a mixture of a potassiferous silicate andcalcareous material to a calcining temperature until calcination ispartly effected, collecting the dust from this operation, resuming theheating until calcination is completed and clinkering etlected andseparately collecting the dust from the sec-- ond heating stage.

11. In the process of making cement clinker and by-products, the processwhich comprises heating a mixture comprising a potassiferous ironsilicate and calcareous material to calcining temperature untilcalcination partly eli'ected, collecting the dust fro)" this operation,resuming the heating until ealcination is completed and clinkeringeffected and separately collecting the dust from the second heatingstage.

12. In the process of making cement clinker and lay-products, theprocess which comprises heating a. mixture comprising glauconite and acalcareous material to a calcining temperature until calcination ispartly ell'ected, collecting'the dust from this operatii'in, resumingthe heating until calcination is completed and clinkering effected andseparately collecting the dust from the second heating stage.

The process of producing cement and potash which comprises heating amixture of a calcareous material and a double silicate of potassium anda cemcntforniing oxid by transmitting the same through a rotary kilnagainst a current of heating gases passing in an opposed direction to-form a cement clinker and fumes of potassium compounds, and collectingthe clinker and the fumes for use.

14. Process of manufacturing simultaneously alkali and hydraulic cement,which consists in mixing, in such condition as to permit chemicalreaction of the ingredients of the mixture when highly heated, alkaliherous mineral matters that contain combined ox'id of an alkali metal,silica and iron with calciferous material at least suliicient to replacethe combined alkali, heating the mixture under such reacting conditionsas to volatilize the alkali as an oxygen compound and leave a residue ofcement material and separately collecting the residue and thevolatilized alkali.

15. The process of simultaneously manufacturing cement clinker andalkali, which comprises mixing a mineral containing a compound ofsilica, a cement forming oxid and a metal of the alkalis with acalciferous material containing oxygen and sutlicient calcium to replacethe alkalimetal and heating the same at a temperature sufficient tocause said replacement and to volatilize the alkali set free and clinkerthe residue.

16. Process of manufacturing simultaneous alkali and hydraulic cement,which consists in mixing, in such condition as to permitcherhicalreaction of the ingredients of the mixture when highly heated,alkaliferous mineral matters that contain combined oxid of alkali metal,silica and a sesquioxid with calciferous material at least sufficient toreplace the combined alkali, heating the mixture under such reactingconditions as to volatilize the alkali as an oxy- -mineral containingsilica, a cement forming oxid and potash with at least enough calcareousmaterial to furnish CaO equivalent to K 0, heating the mixturesutliciently to fume off potash and collecting the potash so fumed oil.

18. The process of simultaneously manufacturing cement clinker andalkali, which comprises reacting, under suitable heat conditions, uponamineral containing a double silicate of iron and an alkali metal, withcalciterous material containing sufficient calcium to replace the alkalimetal in said mineral and capable of setting alkali free, whereby saidalkali will be volatilized, leaving a cement clinker residue.

19. Process of manufacturing simultaneously alkali and hydraulic cement,which consists essentially in mixing in a pulverized state a doublesilicate of cement-forming oxid and an alkali metal, with calciferousmatters containing at least suliicient calcium to replace the combinedalkalimetal and capable of liberating alkali, heating the mixture untilthe alkali is volatilized and the residue forms cement clinker,collecting the alkali and grinding the residue to cement, sub stantiallyas and for the purpose set forth.

20. The process of simultaneously manufacturing cement clinker andalkali, which comprises reacting, under suitable heat conditions, upon amineral containing a double silicate of cement-forming oxid and an al-Kali metal with calciferous material containing suiiicient calcium toreplace the alkali metal in said mineral and capable of setting alkalimetal compounds free, whereby said alkali compounds will be volatilized,leaving a cement clinker residue.

21. In the simultaneous manufacture of alkali and hydraulic cement, theprocess which comprises reacting upon a double silicate ofcement-forming oxid and a metal of the alkalis with a calciferous oxygencompound containing sufficient calcium to replace the alkali metal insaid mineral and capable of liberating the alkali, said. compound beingin quantity suificient to replace substantially all of said alkali metalin themineral, such replacement taking place under sufiicient heating tovolatilize the alkali liberated and leave a residue of cement material,and separately collecting the residue and the volatilized materials.

22. The process of manufacturing simulta-- neously alkali-and hydrauliccement, which comprises reacting upon a double silicate ofcement-forming oxid and a metal of the alkalis, with lime suficientto-replace and liberate alkali, such replacement taking place unders'ufiicient heating to volatilize,

the alkali liberated and leave a residue of cement material andseparately collecting the residueandthe volatilized materials.

23. Process of manufacturing simultaneously alkali and hydraulic cement,which consists essentially in mixing in a pulverized state a doublesilicate of cement-forming oxid and an alkali metal with calciferousmaterial having at least suilicient calcium to replace the combinedalkali metal and capable of liberating alkali metal compounds, heatingthe mixture to the temperature of volatilizing of the alkali metal com.-pounds in'a current of gases which are capable of reacting with thevolatilized alkali compounds to form other alkali metal compounds,collecting the alkali metal combination and grinding the residue tocement, substantially as and'for the purpose set forth.

24. The process of simultaneously manufacturing cement clinker andalkali, which comprises reacting, under suitable heat conditions and inan atmosphere containing fiame'ga'ses upon a mineral material containaing a double silicate of cement-forming oxid and an alkali metal, withcalciferous ma terial containing sufficient calcium to, replace thealkali metal in said mineral material and capable of setting alkalimetal compounds free, whereby said alkali will'be volatilized,

leaving a cement clinker residue.

In testimony whereof, we aili); our signatures in the presence ofwitnesses.

- ARTHUR C. SPENCER. v EDWIN O. ECKEL. -Witnesses for Spencer: WM 0.'Tnr'rs, GAEL S. Hoes.

Witnesses for Eckel:

K. P. MoELnoY, ALBERT 0. WEST.

